Golf ball

ABSTRACT

A golf ball has a plurality of linearly or curvilinearly extending ridge-like lands on its spherical surface. The percent occupation of the total of land areas relative to the overall area of a phantom spherical surface assumed at the level of the top of lands can be reduced to substantially zero.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates to a golf ball having improved flightperformance.

[0003] 2. Background Art

[0004] As is well known in the art, in order that a golf ball which waslaunched gets a long travel distance, the high rebound of the ballitself and the reduced air resistance during flight due to dimplesarranged on the ball surface are crucial factors. A number of methodshave been proposed for arranging dimples on the entire ball surface atas high a density and as uniformly as possible to reduce the airresistance.

[0005] Most often the dimples are recesses or dips of a circular shapeas viewed in plane. Even when the width of a land partitioning twoadjacent dimples is reduced to nearly zero in order to arrange circulardimples at a higher density, the zone surrounded by three or fourdimples becomes a land of generally triangular or tetragonal shapehaving a certain area. Since it is requisite that circular dimples bearranged on the spherical surface as uniformly as possible, the designeffort must reach a certain compromise on the distribution density ofcircular dimples.

[0006] Under the circumstances, it would be desirable to arrange dimplesat a higher density and uniformly. To this end, JP-A 2001-212260proposes that dimples of about two to five types having differentdiameters are arranged on the spherical surface of a ball which isassumed to be a regular octahedron or regular icosahedron.

[0007] However, as long as circular dimples are used, the percentoccupation of the total of dimple areas on the overall spherical surfacearea has a practical limit of about 75% (the total of land areasaccounting for about 25% of the overall spherical surface area). It isthen desired that in order to arrange dimples on the ball surface so asto further reduce the air resistance of the ball in flight, the percentoccupation of the total of dimple areas on the overall spherical surfacearea be further improved.

SUMMARY OF THE INVENTION

[0008] An object of the invention is to provide a golf ball whose flightperformance is improved by increasing the percent occupation of thetotal of dimple areas on the overall spherical surface area.

[0009] Focusing on the shape of lands, the inventor has found that thedesigning of lands to a specific shape enables to substantially reducethe proportion of lands on the spherical surface and to arrange thelands uniformly.

[0010] Accordingly, the invention provides a golf ball comprising aplurality of linearly or curvilinearly extending ridge-like lands on itsspherical surface.

[0011] Preferably, the ridge-like lands are combined to define amultiplicity of cavities. The cavities preferably have a polygonal shapein plane. More preferably, one polygonal cavity has corners at least oneof which is formed with a gap through which the one cavity is incommunication with another polygonal cavity that is disposed adjacent tothe one cavity via a land. Typically, the lands include at least oneshape element selected from I, T, L, H and crisscross shapes.Preferably, the lands have a height of 0.05 to 0.4 mm and a width attheir base of 0.8 to 2.0 mm. Often the total number of lands is 300 to600.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a partial plan view of a golf ball according to oneembodiment of the invention.

[0013]FIG. 2 is a transverse cross-sectional view of a land on the golfball surface, FIG. 2a showing a land of triangular shape, FIG. 2bshowing a land of convergent trapezoidal shape, FIG. 2c showing a landof round top triangular shape, and FIG. 2d showing a land of rectangularshape, in cross section.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring to FIG. 1, there is illustrated in plan view a portionof a golf ball 1 according to one embodiment of the invention. The golfball in the form of a spherical elastic body has a spherical surface 2on which a plurality of discrete, linearly extending ridge-like lands 3are arranged. The ridge-like lands 3 are combined to define amultiplicity of cavities or recesses 4. One cavity 4 is surrounded byseveral lands 3. In this embodiment, the cavities 4 are arrangedsubstantially uniformly over the spherical surface. The lands 3 have alinear shape or I-shape in FIG. 1, but the shape of lands (as viewed inplane) is not limited thereto. The lands may also be constructed by oneor more shape elements including curvilinearly extending shapes such asan arcuate shape and S-shape and variant linear shapes such as T, L, Hand crisscross (+) shapes. Alternatively, such a different shape elementmay be partially incorporated in a land of linear shape or vice versa.It is noted that the term “linearly” or “curvilinearly” extending landmeans that a land extends linearly or curvilinearly as viewed in planeat that land position and as seen in FIG. 1.

[0015] In the golf ball of the invention, each of the lands may have atleast one end 5 in a longitudinal direction thereof as shown in theembodiment of FIG. 1. In the case of an I or L-shaped land, for example,the land has ends on both sides in a longitudinal direction thereof(i.e., two ends). A T-shaped land has three ends. An H orcrisscross-shaped land has four ends.

[0016] In FIG. 1, I-shaped lands 3 are dispersedly distributedsubstantially uniformly over the spherical surface. As a result, fourI-shaped lands define a tetragonal cavity 6 a, and three I-shaped landsdefine a triangular cavity 6 b. The shape of cavities is not limited tothe tetragonal and triangular shapes, and various polygonal shapes maybe defined through choice of the number and arrangement of lands. Inthis regard, the cavity can be constructed as a closed cavity byarranging lands in a closed loop fashion, and such closed cavities maybe partially incorporated in some embodiments. In a preferredembodiment, however, when a cavity is defined by arranging severallands, at least some of the lands are spaced apart to leave a gaptherebetween whereby adjacent cavities are in communication through thegap. In the preferred embodiment of FIG. 1, one cavity has corners (7 a,7 b or 7 c) each formed with a gap (8 a, 8 b or 8 c) through which theone cavity is in communication with another cavity that is disposedadjacent to the one cavity via the land 3. Although a polygonal cavityis provided with gaps at all the corners in the embodiment of FIG. 1because of the I-shaped lands used, the number of gaps per polygonalcavity varies with the shape of lands used.

[0017] The gap which provides communication between two cavitiesdisposed adjacent to each other via a land has a distance t, preferablyin the range of 0.5 to 2 mm.

[0018] The length of lands may be properly selected and vary with theshape of lands. For example, I-shaped lands usually have a length l ofat least 1.0 mm, preferably at least 2.0 mm and up to 8.0 mm, preferablyup to 6.0 mm. If the length l of lands is too large, the distributionbalance of lands may be compromised. If the length l of lands is toosmall, the aerodynamic function of lands may be reduced. It is preferredto use lands of different lengths within the above range in combinationsuch as short, medium and long lands.

[0019]FIG. 2 is a transverse cross-sectional view of a land on the golfball surface, as seen in a section extending radially from the center ofthe ball (not shown).

[0020] The land usually has a height h of usually at least 0.05 mm,preferably at least 0.1 mm and up to 0.4 mm, preferably up to 0.3 mm.Too high a land height h may increase the air resistance whereas too lowa land height h may reduce the arrangement effect. It is preferred thatthe lands have a unity height within the above range.

[0021] The land at its base 32 (joined to the surface 2 of the sphericalbody) usually has a width w of at least 0.8 mm and up to 2.0 mm. Toolarge a land base width w may impair the aerodynamic performance. Withtoo small a land base width w, lands can be broken or damaged uponimpact.

[0022]FIG. 2a shows a land of triangular shape in cross section having atop 31 and a base 32 wherein the width of top 31 is substantially zero.FIG. 2b shows a land of outward convergent trapezoidal shape in crosssection. FIG. 2c shows a land of round top triangular shape in crosssection. FIG. 2d shows a land of rectangular or square shape in crosssection having a top with a width u and a base with a width w wherein uis substantially equal to w. It is preferred to shape lands such thatthe width w at the base is a few times greater than the width u at thetop because such lands are more durable.

[0023] Each land may be formed to the same width or the samecross-sectional shape throughout its longitudinal direction.Alternatively, the land may be formed to varying width as beingconstricted or bulged as long as the objects of the invention are notimpaired.

[0024] When it is desired to arrange the cavities 4 surrounded by thelands 3, shown in FIG. 1, evenly over the spherical surface, onepossible approach is by dividing the spherical surface into surfaceregions of a polyhedron such as an octahedron, dodecahedron oricosahedron, properly arranging the cavities 6 a and 6 b defined bycombinations of lands on each polygonal (or triangular) unit, anddistributing them over the spherical surface. Also, the cavities 4 ofdifferent shapes may be randomly arranged over the spherical surface. Inan alternative procedure, the lands 3 of different shapes are properlyarranged over the spherical surface rather than arranging the cavities4, and as a result of such arrangement, the cavities 4 are concomitantlyformed.

[0025] According to the invention, the proportion of the total of landareas (at the top level of lands) relative to the overall sphericalsurface is reduced to substantially zero or small values approximate tozero, particularly when the lands of cross-sectional shape shown inFIGS. 2a and 2 c are applied. With respect to the type of cavities,there may be used cavities of from one type to about five types,including cavities of different shapes and cavities of the same shape,but of different sizes (areas). The total number of lands (total numberof shape elements including I, T, L, H and + shapes) is preferably from300 to 600 for practical purposes.

[0026] According to the invention, when a phantom spherical surface isassumed at the level of the top of lands, the percent occupation of thetotal of land areas relative to the overall area of the phantomspherical surface can be reduced to substantially zero. Differentlystated, the percent occupation of the total of cavity areas relative tothe overall area of the phantom spherical surface can be increased toapproximately 100% in a substantial sense. As a result, the flightperformance of the golf ball can be dramatically improved.

[0027] Japanese Patent Application Nos. 2002-217637 and 2002-261233 areincorporated herein by reference.

[0028] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A golf ball comprising a plurality of linearly or curvilinearlyextending ridge-like lands on its spherical surface.
 2. The golf ball ofclaim 1 wherein the ridge-like lands are combined to define amultiplicity of cavities.
 3. The golf ball of claim 2 wherein thecavities have a polygonal shape in plane.
 4. The golf ball of claim 3wherein one polygonal cavity has corners at least one of which is formedwith a gap through which the one cavity is in communication with anotherpolygonal cavity that is disposed adjacent to the one cavity via a land.5. The golf ball of claim 1 wherein the lands include at least one shapeelement selected from I, T, L, H and crisscross shapes.
 6. The golf ballof claim 1 wherein the lands have a height of 0.05 to 0.4 mm and a widthat their base of 0.8 to 2.0 mm.
 7. The golf ball of claim 1 wherein thetotal number of lands is 300 to 600.